渭河断陷地壳三维S波速度结构和V_p/ V_s分布图像
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摘要
利用陕西及邻省区域地震台网的观测数据，采用重叠元迭代重建层析成像技术，结合两点快速射线追综，对渭河断陷盆地地壳的Ｓ波速度进行了层析反演成像．并利用前期Ｐ波速度的研究结果，计算了该地区地壳的 Ｖ_ｐ／ Ｖ_ｓ分布．研究结果表明：（１）Ｓ波速度分布两个地区存在强烈的横向不均匀性，其一是陕晋交界的合阳、永济地区，二是铜川、泾阳地区，它们都位于不同构造单元交汇地带，差异运动显著，是新老地层交错的地区．（２）历史强震震中主要分布在Ｓ波的高速区及边缘地带。（３）在淳化、耀县、泾阳之间存在Ｖ_ｐ／Ｖ_ｓ高值区，最高达２．１．
Using the seismic data observed by the seismic networks in Shanxi province and neighbor regions, we studied seismic tomographic imaging of the crustal S wave velocity in the Weihe fault basin by overlapping-shear iterative reconstruction method with the two-points fast ray tracing technique. On the basis of the velocity ratio Vp/ Vs in the same region is calculated. The results show that (1) there are two strong lateral no homogenous regions of S wave velocity distribution, one of which is Heyang-Yongji region on the boundary between Shanxi and Shanxi provinces and the other is Tongchuan-Jingyang zone. Those two areas are located in a region where different tectonic units meet, and differential movement is significant and different rock strata are interceded, (2) the historical strong earthquakes occurred mainly in S wave high-velocity regions on their boundaries; (3) a region with high Vp / Vs value (highest of 2.1) is enclosed by the areas of Chunhua, Yaoxian and Jingyang.
Using the seismic data observed by the seismic networks in Shanxi province and neighbor regions, we studied seismic tomographic imaging of the crustal S wave velocity in the Weihe fault basin by overlapping-shear iterative reconstruction method with the two-points fast ray tracing technique. On the basis of the velocity ratio Vp/ Vs in the same region is calculated. The results show that (1) there are two strong lateral no homogenous regions of S wave velocity distribution, one of which is Heyang-Yongji region on the boundary between Shanxi and Shanxi provinces and the other is Tongchuan-Jingyang zone. Those two areas are located in a region where different tectonic units meet, and differential movement is significant and different rock strata are interceded, (2) the historical strong earthquakes occurred mainly in S wave high-velocity regions on their boundaries; (3) a region with high Vp / Vs value (highest of 2.1) is enclosed by the areas of Chunhua, Yaoxian and Jingyang.
引文
[1]丁韫玉,袁志祥,黄长林.渭河断陷及邻近地区地壳速度图像中国固体地球物理学进展.北京:海洋出版社,1994,55-65DING Yun-Yu, YUAN Zhi-Xiang, HUANG Chang-Lin. The crastal velocity imaging in Weihe fault and itsneighboring region. Advances in Solid Earth Geophysics in China (in Chinese), Beijing: Ocean Press,1994. 55-65.
[2]薛广盈,丁韫玉,袁志祥.渭河断陷盆地地壳速度的层析成像研究.地震学报, 1997, 19(3):283-290XUE Guang-Ying, DING Yun-Yu, YUAN Zhi-Xiang. Study of crustal seismic velocity in the Weihe faultdepression basin by seismic tomographic imaging. Acta Seismologica Sinica (in Chinese), 1997, 19(3): 283-290
[3]袁志祥,薛广盈,丁韫玉等.渭河断陷及邻近地区莫霍界面速度图像.地震地质,1995,17(4):446-452.YUAN Zhi-Xiang, XUE Guang-Ying, DING Yun-Yu, et al. Seismic velocity image of Moho discontinuity beneath Weihe fault depression and its adjacent areas. Seismology and Geology (in Chinese), 1995, 17(4):446-452.
[4]王椿镛,丁志峰,宋建立等.大别造山带地壳S波速度结构.地球物理学报,1997,40(3):320-345WANG Chun-Yong, DING Zhi-Feng, SONG Jian-Li, et al. Shear wave velocity structure in Debieshanorogenic belt. Chinese J. Geophys (in Chinese), 1997, 40(3):330-345.
[5]宋松岩,周雪松,王椿镛等.泰安一忻州剖面S波资料解释及其与邢台地震的相关性分析.地震学报,1997,19(1):13-21.SONG Song-Yan, ZHOU Xue-Song, WANG Chun-Yong, et al. Taian-Xinzhou DSS profile and itsrelationship with Xingtai earthquakes. Acta Seismologica Sinica (in Chinese), 1997, 19(1): 13-21.
[6] Nichoison C, D W Simpson. Changes in Vp / Vs with depth: Implications for appropriate velocity models,improved earthquake locations, and material properties of the upper crust, Bull. Seism. Soc. Am., 1985,75(4). 1105-1124.
[7] Marianne C Walek. Three-dimensional Vp / Vs variations for the Coso region, California.J. Geophys. Res.,1988, 93(B3): 2047-2052.
[8] Greenhalgh S A, Sugiharto S, Wright C, et al. Tomographic reconstruction of upper crustal velocityvariations in the Arunta block, Central Australia. Tectonophysics,1990, 173: 63-72.
[9] Um J, Thurber C. A fast algorithm for two-point seismic ray tracing. Bull.Seism. Soc. Am., 1987, 77(3):972-986.
[10] Peterson J E, Paulsson B N, McEevilly T V. Applications of algebraic reconstruction techniques to crosshole seismic data. Geophysics,1985, 50(10). 1566-1580.
[11]薛广盈,冯锐利用首波重建基底速度图像.地震地质, 1990,12(2): 141-148XUE Guang-Ying, FENG Rui. Reconstruction of the basement velocity image based on head wave.Seismology and Geology (in Chinese), 1990, 12(2). 141-148.
[12]孙若昧,赵燕来,梅世蓉.渤海及其邻区的地震层析成像地球物理学报,1993,36(1):44-54.SUN Ruo-Mei, ZHAO Yan-Lai, MEI Shi-Rong. Seismic tomographic image in Bohai Sea and its adjacentarea. Chinese J. Geophys (in Chinese), 1993, 36(1): 44-54.
[13] Robert H Tatham. Vp / Vs and lithology. Geophysics,1982, 47(3): 336-344.
[2]薛广盈,丁韫玉,袁志祥.渭河断陷盆地地壳速度的层析成像研究.地震学报, 1997, 19(3):283-290XUE Guang-Ying, DING Yun-Yu, YUAN Zhi-Xiang. Study of crustal seismic velocity in the Weihe faultdepression basin by seismic tomographic imaging. Acta Seismologica Sinica (in Chinese), 1997, 19(3): 283-290
[3]袁志祥,薛广盈,丁韫玉等.渭河断陷及邻近地区莫霍界面速度图像.地震地质,1995,17(4):446-452.YUAN Zhi-Xiang, XUE Guang-Ying, DING Yun-Yu, et al. Seismic velocity image of Moho discontinuity beneath Weihe fault depression and its adjacent areas. Seismology and Geology (in Chinese), 1995, 17(4):446-452.
[4]王椿镛,丁志峰,宋建立等.大别造山带地壳S波速度结构.地球物理学报,1997,40(3):320-345WANG Chun-Yong, DING Zhi-Feng, SONG Jian-Li, et al. Shear wave velocity structure in Debieshanorogenic belt. Chinese J. Geophys (in Chinese), 1997, 40(3):330-345.
[5]宋松岩,周雪松,王椿镛等.泰安一忻州剖面S波资料解释及其与邢台地震的相关性分析.地震学报,1997,19(1):13-21.SONG Song-Yan, ZHOU Xue-Song, WANG Chun-Yong, et al. Taian-Xinzhou DSS profile and itsrelationship with Xingtai earthquakes. Acta Seismologica Sinica (in Chinese), 1997, 19(1): 13-21.
[6] Nichoison C, D W Simpson. Changes in Vp / Vs with depth: Implications for appropriate velocity models,improved earthquake locations, and material properties of the upper crust, Bull. Seism. Soc. Am., 1985,75(4). 1105-1124.
[7] Marianne C Walek. Three-dimensional Vp / Vs variations for the Coso region, California.J. Geophys. Res.,1988, 93(B3): 2047-2052.
[8] Greenhalgh S A, Sugiharto S, Wright C, et al. Tomographic reconstruction of upper crustal velocityvariations in the Arunta block, Central Australia. Tectonophysics,1990, 173: 63-72.
[9] Um J, Thurber C. A fast algorithm for two-point seismic ray tracing. Bull.Seism. Soc. Am., 1987, 77(3):972-986.
[10] Peterson J E, Paulsson B N, McEevilly T V. Applications of algebraic reconstruction techniques to crosshole seismic data. Geophysics,1985, 50(10). 1566-1580.
[11]薛广盈,冯锐利用首波重建基底速度图像.地震地质, 1990,12(2): 141-148XUE Guang-Ying, FENG Rui. Reconstruction of the basement velocity image based on head wave.Seismology and Geology (in Chinese), 1990, 12(2). 141-148.
[12]孙若昧,赵燕来,梅世蓉.渤海及其邻区的地震层析成像地球物理学报,1993,36(1):44-54.SUN Ruo-Mei, ZHAO Yan-Lai, MEI Shi-Rong. Seismic tomographic image in Bohai Sea and its adjacentarea. Chinese J. Geophys (in Chinese), 1993, 36(1): 44-54.
[13] Robert H Tatham. Vp / Vs and lithology. Geophysics,1982, 47(3): 336-344.
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